The invention concerns a device for cooling hot gases. The gases derive from incomplete oxidation in a reactor and are loaded with solids.
Contemporary fly-stream gasification methods are expected to gasify a multivalent range of fuels. This expectation, however, is considerably frustrated by downstream cooling processes that use a lot of energy. Heat-removal systems that efficiently exploit the apparent heat of the unprocessed gas for a specific range of fuels are known. These systems use either a refrigerator (German Patent 3 147 864) to achieve efficient heat utilization or a quencher (German Patent 2 940 933) to cool the unprocessed gas at least to some extent.
The refrigerator is accommodated in a container with a bath of water in the bottom. The bath intercepts and agglomerates tacky particles of ash entrained by the new gas. Another known device (German Patent 2 951 153) cools and cleans a synthesis gas derived from goal gasification. Some or all of the gas is forced through water and extracted through an outlet. The temperature of the gas, which is supplied to a downstream heat-removal boiler, varies extensively. The bath is as high as the gas outlet. The gas traveling through the bath picks up as intended the water it will need for chemical reactions during subsequent processing of the gas. It is, however, impossible to prevent the water from forming droplets within the unprocessed gas. Such droplets can cause malfunctions in the downstream equipment. There is a heat exchanger in the bath that regulates the water temperature to a considerable extent and prevents it from evaporating as the gas travels through it.
Fly-stream gasification is carried out at a high temperature, and necessarily utilizes, especially for the combination gas-and-steam turbine process, the unprocessed gas's apparent heat to generate the current. That heat accounts for approximately 20% of the power plant's efficiency. Gasification must completely convert as much of the carbon in the fuel as possible. The temperature of the gas leaving the gasification reactor will accordingly essentially depend on ash fluidics. The gas can accordingly enter the downstream heat-removal equipment at temperatures higher than 1800.degree. C. Malfunctions in the downstream equipment can derive from the molten slag or, depending on how the process is conducted, from tacky particles entrained by the gas. To prevent such problems the unprocessed gas must be cooled down to approximately 700.degree. to 1000.degree. C., preferably in a refrigerator.
When some fuels, saliniferous brown coal for example, are employed, it is impossible to cool the gas further in a convective heat remover downstream of the refrigerator. Sublimates from the fuel would invade the unprocessed gas and could unacceptably contaminate the heating surfaces. In this event the gas can be cooled only with a quencher, preferably by immersion. Saliniferous brown coals have until now been successfully gasified only by fly streaming followed by immersion quenching.